This invention relates to a magnetic disk used for a magnetic disk apparatus such as HDD (hard disk drive) and, in particular, to a method of manufacturing the magnetic disk as well as a method of evaluating the magnetic disk.
Recently, in an information recording technique, in particular, in a magnetic recording technique, a drastic technical innovation is required following development of an IT industry. In a magnetic disk loaded in a magnetic disk apparatus such as a HDD (hard disk drive), an information recording density has been rapidly increased unlike in other magnetic recording media such as a magnetic tape and a flexible disk.
The magnetic disk comprises a nonmagnetic substrate and a magnetic layer formed thereon for recording information. On the magnetic layer, a protection layer is provided so as to protect the magnetic layer. On the protection layer, a lubricant layer is disposed so as to relieve interference from a magnetic head for carrying out recording and reproducing operations while flying over the magnetic disk. Such a magnetic disk is, for example, disclosed in Japanese Unexamined Patent Application Publication (JP-A) No. 6-195691 (see FIG. 6, hereinafter referred to as a patent document 1) and is known in the art.
As the protection layer of the magnetic disk, use is typically made of a hydrogenated carbon film which is deposited by sputtering a carbon target in an atmosphere of a mixed gas of an Ar (argon) gas and a hydrogen gas or a mixed gas of an Ar gas and a hydrocarbon gas (for example, methane gas).
In the hydrogenated carbon film, by adjusting a depositing method and a depositing condition, it is possible to relatively freely adjust mechanical characteristics such as a CSS (Contact Start Stop) durability. Therefore, the hydrogenated carbon film is widely used as the protection layer of the magnetic disk.
In order to obtain the protection layer having desired mechanical characteristics, it is conceivable to prepare a plurality of samples of magnetic disks by depositing sample protection layers in various manufacturing conditions, to evaluate the mechanical characteristics such as the CSS durability for these samples of magnetic disks, and to determine the manufacturing condition of the magnetic disk to be manufactured.
However, determination of the manufacturing condition using the above-mentioned method requires much time and labor and is troublesome. It is therefore impossible to quickly determine the manufacturing condition and the manufacturing cost is inevitably increased.
In view of the above, it has heretofore been attempted to find film quality parameters associated with the mechanical characteristics of the protection layer and to measure the film quality parameters by simple means, thereby maintaining the mechanical characteristic of the protection layer in the magnetic disk to be manufactured.
For example, the aforementioned patent document 1 discloses a method of evaluating the film quality of the protection layer by utilizing a peak intensity of a SP3 peak (D peak) and a peak intensity of a SP2 peak (G peak) in a Raman spectrum of the protection layer. Specifically, according to this technique, a ratio (B/A) of peak intensities is used as an evaluation basis where A represents a substantial peak intensity excluding photoluminescence at a wavenumber of the SP3 peak (D peak) and B represents a total peak intensity including the photoluminescence at the SP3 peak. Further, according to this technique, a ratio (D/G) of peak intensities is used as an evaluation basis where D represents a substantial peak intensity excluding photoluminescence at the wavenumber of the SP3 peak (D peak) and G represents a substantial peak intensity excluding photoluminescence at the wavenumber of the SP2 peak (G peak).
Moreover, Japanese Unexamined Patent Application Publication (JP-A) No. 6-267063 (see FIG. 1, hereinafter referred to as a patent document 2) and Japanese Unexamined Patent Application Publication (JP-A) No. 7-192254 (see FIG. 1, hereinafter referred to as a patent document 3) disclose a method of evaluating the film quality of the protection layer by using, as an evaluation basis, an area ratio (B/A) at half widths of waveforms of a SP3 peak (D peak) and a SP2 peak (G peak) in the Raman spectrum of the protection layer.